A venture of CIM Group has agreed to pay about $48 million for the 27-story office tower at 625 N. Michigan Ave., or 17 percent more than its sale price two years ago, according to people familiar with the deal. The sale does not include the lower four floors, which are separately owned retail space.

Chicago-based Golub & Co., which partnered with New York-based seller Goldman Sachs Group on the 2013 acquisition, will stay in the deal and maintain a minority ownership stake with CIM.

Tribeca Holdings London, a venture of Irish investor Aidan Brooks that invests in retail real estate, bought 625 N. Michigan for $107 million in June 2013 and immediately divided up the property into four lower floors of retail and an office property that it flipped to the Goldman Sachs venture for $41 million, according to Cook County records.

Tribeca bought the property from San Francisco-based Wells Fargo Bank, which seized it from a venture of Golub and now-defunct Anglo Irish Bank after that venture defaulted on a $103 million loan during the real estate slump.

A CIM spokeswoman declined to comment. Golub Executive Vice President Lee Golub and a Goldman Sachs spokeswoman each did not return a call.

The office portion of the building at Michigan Avenue and Ontario Street has 289,897 rentable square feet and is 29 percent vacant, according to materials from the Chicago office of HFF, which is brokering the sale. The tower was built in 1970 and underwent a $6 million renovation in 2000, according to the HFF flier.

MICHIGAN AVENUE OFFICE VACANCY

Floors are about 13,000 square feet, and no tenant takes up more than one full floor, according to real estate data provider CoStar Group.

While North Michigan Avenue retail is coveted, its office space lags the overall downtown market. During the second quarter, when downtown vacancy dipped to its lowest level since 2008 at 13.3 percent, North Michigan Avenue office vacancy was 15.6 percent, according to Los Angeles-based CBRE. That was higher than every downtown submarket except for the East Loop's 16 percent.

But the deal for 625 N. Michigan allows CIM to break into the Chicago office market, where it has been scouting acquisitions amid intense competition from other buyers, real estate sources said.

At midyear, a combined $4.19 billion worth of office buildings had sold downtown, on pace to shatter the record $5.3 billion mark from 2006. This year's high volume has included New York-based Blackstone Group's Chicago-record $1.3 billion deal for Willis Tower and a pending $712 million acquisition of the 83-story Aon Center by a venture New York-based 601W Cos.